Massachusetts Sen. Elizabeth Warren took a major step toward a presidential run on Monday, announcing in a video message and email to supporters that she is forming an exploratory committee ahead of an expected campaign for the Democratic nomination in 2020.

With her announcement 13 months before the Iowa caucuses, Warren, who became a progressive star by taking on Wall Street after the 2007 financial crisis and, more recently, President Donald Trump, is the first Democrat with a national profile to take formal action towards a likely presidential campaign.

In a four-and-a-half minute video, Warren makes clear some of the very themes that catapulted her to national prominence will define her upcoming presidential run: economic equality, government accountability and reining in big corporations.

“Corruption is poisoning our democracy,” Warren says in the video as images of Republican leaders flash across the screen. “Politicians look the other way while big insurance companies deny patients life-saving coverage, while big banks rip off consumers and while big oil companies destroy this planet.”

The clip begins with the senator recalling a hardscrabble childhood in Oklahoma — her mother got a minimum-wage job after her father suffered a heart attack. He would eventually work as a janitor.

“He raised a daughter who got to be a public school teacher, a law professor and a senator. We got a real opportunity to build something,” Warren says. “Working families today face a lot tougher path than my family did.”

In one of multiple nods in the video to racial inequality, she adds that “families of color face a path that is steeper and rockier, a path made even harder by the impact of generations of discrimination” — an early acknowledgment of the political importance of appealing to and winning the support of minority voters.

As she warns of a deepening crisis faced by the American middle class, Warren points a finger squarely at the Republican Party, using images of former presidents Ronald Reagan and George W. Bush, along with grinning cameos from Treasury Secretary Steven Mnuchin, departing House Speaker Paul Ryan, Senate Majority Leader Mitch McConnell and Trump.

Warren is a searing critic of the President, and Trump has responded by openly mocking her Native American heritage and referring to her as “Pocahontas.” Her decision in October to respond to Trump and other critics by releasing the results of a DNA test aimed at proving her ancestry fell flat with many Democrats and overshadowed her midterm message.

The announcement also comes in the midst of a prolonged partial government shutdown over Trump’s insistence on funding for a border wall, which has caused political chaos that has spooked investors and sparked turmoil in the stock market. This backdrop could prove to be a boon for Warren, who is widely expected to build a campaign centered around her signature economic populist message and anti-corruption platform.

By launching an exploratory committee, Warren can begin raising money for the coming campaign. She is unlikely to seek the assistance of a billionaire-funded super PAC, according to a source familiar with Warren’s thinking, because she believes grassroots support should be a defining factor in the coming primary. Warren has already sworn off corporate PAC money.

Even before Monday’s notifications went out, the work of building the infrastructure to support a presidential bid had been well underway.

Since her re-election to the Senate in November, Warren has made hundreds of calls to political grassroots leaders in the early states of Iowa, New Hampshire, South Carolina and Nevada, the source said.

Warren’s staff members are also having discussions with operatives in those states and are in the process of searching for campaign office space in the Boston area, the expected location of her presidential campaign headquarters.

Dan Geldon, Warren’s longtime aide who served as her chief of staff in the Senate and was once the senator’s student at Harvard Law School, is likely to serve a senior role in the eventual Warren campaign, the source said.

More than a year out from the first round of voting and with months to go until the first debate, the coming Democratic primary is already shaping up to be one of the most fierce and feisty nominating contests in a generation.

Warren’s work to establish and defend the Consumer Financial Protection Bureau, or CFPB, made her a star among progressives who first pushed for what would be a successful 2012 Senate run and then, with less luck, a presidential bid she ultimately passed up four years later.

This time around, the large Democratic field is expected to include multiple candidates touting progressive platforms — a reality that underscores her influence within the party but could also complicate her path to its nomination.

Some two dozen candidates are said to have shown interest in a 2020 bid. Warren’s national profile, which traces back to her work as a watchdog following the 2008 bank bailouts, immediately places her among the favorites, alongside former Vice President Joe Biden, Vermont Sen. Bernie Sanders and rising star Beto O’Rourke, the departing Texas congressman who just lost a bid for the US Senate.

Her decision to more formally begin the process comes less than a month after the editorial board for her hometown newspaper, the Boston Globe, ruffled progressive feathers by suggesting she consider abandoning a potential run.

“Warren missed her moment in 2016, and there’s reason to be skeptical of her prospective candidacy in 2020,” the board wrote in early December, citing a poll from September 2018 that put former Massachusetts Gov. Deval Patrick, a Democrat who has since ruled out a presidential run this cycle, ahead of Warren.

It also suggested she had become too much of a “divisive figure,” an apparent reference to the heavily publicized DNA test. It confirmed Warren had distant Native American ancestry, but was met with backlash from some tribal leaders, activists and outspoken Democrats who fretted over whether Warren had played into Trump’s hands.

Cherokee Nation Secretary of State Chuck Hoskin Jr. was among the most outspoken critics and said Warren had undermined “tribal interests.”

“Using a DNA test to lay claim to any connection to the Cherokee Nation or any tribal nation, even vaguely, is inappropriate and wrong,” Hoskin said in a statement.

But any early missteps — or even disappointing polling — are unlikely to dampen excitement among the party’s increasingly influential progressive bloc.

“Elizabeth Warren, on a visceral level, is fighting for everyday people and against powerful interests,” Progressive Change Campaign Committee co-founder Adam Green said, “and that comes through with an authenticity this moment demands.”

Green, whose group has supported Warren for years while talking up “the Warren wing” of the Democratic party, also gave a hint of how his group and potentially others might seek to distinguish the Massachusetts senator from other leading contenders.

“There are different theories on being effective, but she believes in picking issues that are super popular and forging coalitions to win on those issues,” he said. “Others can be more of a loner, or willing to charge into battle first before having a fully baked plan.”